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> > To view this discussion on the web visit
> > [https://groups.google.com/d/msgid/elasticsearch/0d204979-3403-4b07-9782-c4b52120f7e9%40googlegroups.com](https://groups.google.com/d/msgid/elasticsearch/0d204979-3403-4b07-9782-c4b52120f7e9%40googlegroups.com)
> > [https://groups.google.com/d/msgid/elasticsearch/0d204979-3403-4b07-9782-c4b52120f7e9%40googlegroups.com?utm\_medium=email&utm\_source=footer](https://groups.google.com/d/msgid/elasticsearch/0d204979-3403-4b07-9782-c4b52120f7e9%40googlegroups.com?utm_medium=email&utm_source=footer)
> > .
> > For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout).
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### Author:  [@jpountz](https://discuss.elastic.co/u/jpountz)
#### Post date: [October 7, 2014, 4:33pm UTC](https://discuss.elastic.co/t/understanding-doc-values/20114/4 "2014-10-07T16:33:45Z")
Hi Michaël,
Doc values just mean that field data will be computed at indexing time and
stored on disk as opposed to computed at search time (which is the
default). You can expect them to be slightly slower, but they have
significant benefits too: their memory footprint is low, since most stuff
is stored on disk. In particular this will help with other issues such as
garbage collection. And since they are computed at indexing time, you don't
have the same cold start issue that you can have with in-memory fielddata
since recomputing them from the inverted index is both CPU and I/O
intensive. We initially added doc values support in 1.0 but they got better
and better with each release (especially in the forthcoming 1.4 release)
and we are even thinking about making them the default in a future release
(nothing decided yet, just thinking about it).
On Tue, Oct 7, 2014 at 5:19 PM, Michaël Gallego [michael@maestrooo.com](mailto:michael@maestrooo.com)
wrote:
> I'm using a machine with fast SSD so it should be ok.
>
> I'm not sure to udnerstand the downside "you cannot filter". What do you
> mean exactly? I tried to do a range filter on the value, and it indeed
> works!
>
> Le mardi 7 octobre 2014 16:23:41 UTC+2, Ivan Brusic a écrit :
>
> > Perhaps it is easier to talk about the downsides of doc\_values.
> >
> > If you have slow disks, common when using low level VMs with shared
> > disks, then retrieving your data will be much slower.
> >
> > Also, you cannot filter on doc\_values fields, so it depends on your other
> > use cases.
> >
> > The amount field seems like a good candidate for doc\_values, but it
> > depends on the downsides I highlighted above.
> >
> > Cheers,
> >
> > Ivan
> > On Oct 7, 2014 6:11 AM, "Michaël Gallego" [mic...@maestrooo.com](mailto:mic...@maestrooo.com) wrote:
> >
> > > Hi,
> > >
> > > With the release of Elasticsearch 1.4, I discovered about doc\_values.
> > > However their use remains a bit obscure for me, and the documentation
> > > didn't help. As I understand it, it is mostly useful when performing
> > > aggregations, as it allows to reduce the memory amount of data loaded in
> > > memory. The doc recommends to specify not\_analyzed string as doc\_values, as
> > > well as values that are used for aggregations. But for instance, if my
> > > aggregations are about summing one value called "amount", does it make the
> > > "amount" integer/double as a good candidate for doc\_values, or is it only
> > > useful for properties that are space consuming?
> > >
> > > In overall, if my use case is nearly only aggregations, should I go the
> > > way of setting all proeprties as doc\_values, except the analyzed strings?
> > >
> > > Thanks!
> > >
> > > --
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> > > msgid/elasticsearch/0d204979-3403-4b07-9782-c4b52120f7e9%
> > > [40googlegroups.com](http://40googlegroups.com)
> > > [https://groups.google.com/d/msgid/elasticsearch/0d204979-3403-4b07-9782-c4b52120f7e9%40googlegroups.com?utm\_medium=email&utm\_source=footer](https://groups.google.com/d/msgid/elasticsearch/0d204979-3403-4b07-9782-c4b52120f7e9%40googlegroups.com?utm_medium=email&utm_source=footer)
> > > .
> > > For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout).
> >
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> > [https://groups.google.com/d/msgid/elasticsearch/45292b0b-659e-418c-9eee-e6d3bff23abf%40googlegroups.com?utm\_medium=email&utm\_source=footer](https://groups.google.com/d/msgid/elasticsearch/45292b0b-659e-418c-9eee-e6d3bff23abf%40googlegroups.com?utm_medium=email&utm_source=footer)
> > .
>
> For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout).
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### Author:  [@Michael\_Gallego\_2](https://discuss.elastic.co/u/Michael_Gallego_2)
#### Post date: [October 9, 2014, 12:13pm UTC](https://discuss.elastic.co/t/understanding-doc-values/20114/5 "2014-10-09T12:13:20Z")
Hi again,
I've tried to create two types and fill them with data that mimic my own
data, both with doc\_values for all non-analyzed string and numeric fields
and without doc\_values. My additional question is to know if there are some
overhead of mixing both doc\_values and non-doc values inside the same
document, or it does not matter?
On my small machine and Elasticsearch 1.3, doc\_values is approximately 25%
slower, if 1.4 makes this much better, I think I'll use them. However, the
question is: how can I actually benchmark this? I didn't find any way to
profile my aggregation queries to see things like memory consumption taken
by one query. Without this information, how can I know some important
metrics that would help me to choose between doc\_values and without
doc\_values?
Thanks a lot!
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### Author:  [@jpountz](https://discuss.elastic.co/u/jpountz)
#### Post date: [October 9, 2014, 2:50pm UTC](https://discuss.elastic.co/t/understanding-doc-values/20114/6 "2014-10-09T14:50:51Z")
It is perfectly fine to have some fields that have doc values and other
fields that don't.
Doc values are indeed faster in 1.4, especially on numeric fields. Using
doc values doesn't change the memory usage of aggregations. However, it
will change the memory usage for field data. It's a bit tricky to track
today because doc values are not accounted in "fielddata" but in the
"segments"[1] memory usage.
[1]
> **[Elasticsearch Platform — Find real-time answers at scale](https://www.elastic.co)**
>
> Power insights and outcomes with the Elasticsearch Platform and AI. See into your data and find answers that matter with enterprise solutions designed to help you build, observe, and protect. Try Elasticsearch free today.
On Thu, Oct 9, 2014 at 2:13 PM, Michaël Gallego [michael@maestrooo.com](mailto:michael@maestrooo.com)
wrote:
> Hi again,
>
> I've tried to create two types and fill them with data that mimic my own
> data, both with doc\_values for all non-analyzed string and numeric fields
> and without doc\_values. My additional question is to know if there are some
> overhead of mixing both doc\_values and non-doc values inside the same
> document, or it does not matter?
>
> On my small machine and Elasticsearch 1.3, doc\_values is approximately 25%
> slower, if 1.4 makes this much better, I think I'll use them. However, the
> question is: how can I actually benchmark this? I didn't find any way to
> profile my aggregation queries to see things like memory consumption taken
> by one query. Without this information, how can I know some important
> metrics that would help me to choose between doc\_values and without
> doc\_values?
>
> Thanks a lot!
>
> --
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> [https://groups.google.com/d/msgid/elasticsearch/fee91837-0f29-4268-9391-c3581ce4b70b%40googlegroups.com?utm\_medium=email&utm\_source=footer](https://groups.google.com/d/msgid/elasticsearch/fee91837-0f29-4268-9391-c3581ce4b70b%40googlegroups.com?utm_medium=email&utm_source=footer)
> .
>
> For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout).
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Adrien Grand
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### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [July 6, 2017, 12:57am UTC](https://discuss.elastic.co/t/understanding-doc-values/20114/7 "2017-07-06T00:57:17Z")